Isa 6:8-10 And I heard the voice of the Lord saying, "Whom shall I send, and who will go for us?" Then I said, "Here I am! Send me. And he said, "Go, and say to this people: "'Keep on hearing, but do not understand; keep on seeing, but do not perceive.' Make the heart of this people dull, and their ears heavy, and blind their eyes; lest they see with their eyes, and hear with their ears, and understand with their hearts, and turn and be healed." (Also Acts 28:27)

Mat 13:13 This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand.

Mat 13:43 Then the righteous will shine like the sun in the kingdom of their Father. He who has ears, let him hear.

Mar 4:9 And he said, "He who has ears to hear, let him hear."

Mar 4:23 If anyone has ears to hear, let him hear."

Mar 8:18 Having eyes do you not see, and having ears do you not hear? And do you not remember?

Luk 8:8 And some fell into good soil and grew and yielded a hundredfold." As he said these things, he called out, "He who has ears to hear, let him hear."

Luk 14:35 It is of no use either for the soil or for the manure pile. It is thrown away. He who has ears to hear, let him hear.”

Heb 5:11 About this we have much to say, and it is hard to explain, since you have become dull of hearing.

Rev 2:7 He who has an ear, let him hear what the Spirit says to the churches. To the one who conquers I will grant to eat of the tree of life, which is in the paradise of God.'

Rev 2:11 He who has an ear, let him hear what the Spirit says to the churches. The one who conquers will not be hurt by the second death.'

Rev 2:17 He who has an ear, let him hear what the Spirit says to the churches. To the one who conquers I will give some of the hidden manna, and I will give him a white stone, with a new name written on the stone that no one knows except the one who receives it.'

Rev 2:29 He who has an ear, let him hear what the Spirit says to the churches.'

Rev 3:6 He who has an ear, let him hear what the Spirit says to the churches.'

Rev 3:13 He who has an ear, let him hear what the Spirit says to the churches.'

Rev 3:22 He who has an ear, let him hear what the Spirit says to the churches.'"

Rev 13:9 If anyone has an ear, let him hear...

Given the preponderance of scriptural evidence that God's people often become hard of hearing, I beg you...GUARD YOUR EARS.